Method and control devices for production of consistent water quality from membrane-based water treatment for use in improved hydrocarbon recovery operations

ABSTRACT

A method for treating water including intaking a first amount of water from a first source into a plurality of treatment blocks, treating the first amount of water, outputting aqueous treated water streams from each of the plurality of treatment blocks, separating the aqueous treated water streams from each of the plurality of treatment blocks into aqueous permeate streams and concentrate reject streams, monitoring each of the aqueous permeate streams, controlling the operation of at least one of the plurality of treatment blocks based on predefined water-characteristic tolerances that fall within a predetermined concentration range based on the different qualities of the aqueous permeate streams, outputting a product water stream into an injection water reservoir or blend point, the product water stream including the aqueous permeate stream, intaking a second amount of water from a second source, treating the second amount of water, and discharging the dischargeable water stream.

BACKGROUND

Field of the Invention

Embodiments disclosed herein relate generally to methods and controldevices for production of consistent water quality from membrane-basedwater treatment for use in improved hydrocarbon recovery operations.

Background Art

Hydrocarbons accumulated within a subterranean hydrocarbon-bearingformation are recovered or produced therefrom through production wellsdrilled into the subterranean formation. When production of hydrocarbonsslows, improved recovery techniques may be used to force thehydrocarbons out of the formation. One of the simplest methods offorcing the hydrocarbons out of the formation is by direct injection offluid into the formation. This enhances production by displacing orsweeping hydrocarbons through the formation so that they may be producedfrom production well(s).

As shown in FIG. 1, a prior art system for recovering hydrocarbons froma formation consists of an offshore rig 12 connected to a well 10, whichis completed in a subterranean hydrocarbon-bearing formation 14.Generally, fluid is injected directly into the subterraneanhydrocarbon-bearing formation 14 (indicated by the down arrow) andforces the hydrocarbons through the formation and out of the well 10(indicated by the up arrow) via a production well, which may be the sameor a different well. One type of such recovery operation uses water(e.g., seawater, produced water) as the injection fluid, which isreferred to as a waterflood. Water is injected, under pressure, into theformation via injection wells, driving the hydrocarbons through theformation toward production wells.

Injection water used in waterflooding for offshore wells is typicallyseawater and/or produced water because of the low-cost availability ofseawater and/or produced water at offshore locations. Another motivationfor using produced water as an injection water offshore is thedifficulty in some locations in disposing the produced water offshore.In any case, seawater and produced water are generally characterized assaline, having a high ionic content relative to fresh water. Forexample, the fluids are rich in sodium, chloride, sulfate, magnesium,potassium, and calcium ions, to name a few. Some ions present ininjection water can benefit hydrocarbon production. For example, certaincombinations of cations and anions, including K⁺, Na⁺, Cl⁻, Br⁻, andOH⁻, can stabilize clay to varying degrees in a formation susceptible toclay damage from swelling or particle migration.

However, it has also been found that certain ions, including calciumand/or sulfate, present in the injection water may have harmful effectson the injection wells and production wells and can ultimately diminishthe amount or quality of the hydrocarbon product produced from theproduction wells. Specifically, sulfate ions can form salts in situ whencontacted with metal cations such as barium and/or strontium, which maybe naturally occurring in the reservoir. Barium and strontium sulfatesalts are relatively insoluble and readily precipitate out of solutionunder ambient reservoir conditions. Solubility of the salts furtherdecreases as the injection water is produced to the surface with thehydrocarbons because of temperature decreases in the production well.The resulting precipitates accumulate as barium sulfate scale in theoutlying reservoir, at the wellbore of the hydrocarbon production wells,and downstream thereof (e.g., in flow lines, gas/liquid separators,transportation pipelines, etc). The scale reduces the permeability ofthe reservoir and reduces the diameter of perforations in wellbores,thereby diminishing hydrocarbon recovery from the hydrocarbon productionwells. Divalent cations are particularly effective at stablizingsensitive clays.

It has also been reported that a significant concentration of sulfateions in injection water promotes reservoir souring. Reservoir souring isan undesirable phenomenon whereby reservoirs are initially sweet upondiscovery, but turn sour during the course of waterflooding andattendant hydrocarbon production from the reservoir. Souringcontaminates the reservoir with hydrogen sulfide gas or othersulfur-containing species and is evidenced by the production ofquantities of hydrogen sulfide gas along with the desired hydrocarbonfluids from the reservoir via the hydrocarbon production wells. Thehydrogen sulfide gas causes a number of undesired consequences at thehydrocarbon production wells and downstream of the wells, includingexcessive degradation and corrosion of the hydrocarbon production wellmetallurgy and associated production equipment, diminished economicvalue of the produced hydrocarbon fluids, an environmental hazard to thesurroundings, and a health hazard to field personnel.

The hydrogen sulfide is believed to be produced by an anaerobicsulfate-reducing bacteria. The sulfate-reducing bacteria is oftenindigenous to the reservoir and is also commonly present in theinjection water. Sulfate ions and organic carbon are the primary feedreactants used by the sulfate reducing bacteria to produce hydrogensulfide in situ. The injection water is usually a plentiful source ofsulfate ions, while formation water is a plentiful source of organiccarbon in the form of naturally-occurring low molecular weight fattyacids. The sulfate reducing bacteria effects reservoir souring bymetabolizing the low molecular weight fatty acids in the presence of thesulfate ions, thereby reducing the sulfate to hydrogen sulfide. Statedalternatively, reservoir souring is a reaction carried out by thesulfate reducing bacteria which converts sulfate and organic carbon tohydrogen sulfide and byproducts.

A number of strategies have been employed in the prior art forremediating reservoir souring with limited effectiveness. These priorart strategies have primarily been single pronged attacks against eitherthe sulfate reducing bacteria itself or against a specific food nutrientof the sulfate reducing bacteria. For example, many prior art strategieshave focused on killing the sulfate reducing bacteria in the injectionwater or within the reservoir. Conventional methods for killing thesulfate reducing bacteria or limiting their growth may includeultraviolet light, biocides, and chemicals such as acrolein andnitrates. Other prior art strategies for remediating reservoir souringhave focused on limiting the availability of sulfates or organic carbonto the sulfate reducing bacteria.

More recently, strategies for remediating reservoir souring haveincluded the use of membranes to reduce the concentration of sulfateions in injection water. For example, U.S. Pat. No. 4,723,603 shows thatspecific membranes can effectively reduce the concentration of sulfateions in injection water, thereby inhibiting sulfate scale formation. Astaught by the prior art, nanofiltration (NF) membranes are oftenpreferred to reverse osmosis (RO) membranes because nanofiltrationmembranes generally permit a higher passage of sodium chloride comparedto reverse osmosis membranes. Consequently, nanofiltration membranes areadvantageously operable at substantially lower pressures and operatingcosts than reverse osmosis membranes. Furthermore, nanofiltrationmembranes also maintain the ionic strength of the resulting injectionwater at a relatively high level, which desirably reduces the risk ofclay instability and correspondingly reduces the risk of waterpermeability loss through the porous substrata of the subterraneanformation.

However, in addition to the problems associated with sulfate ions beingpresent in the injection water, it has also been found that the salinityof an injection water can have a major impact on the recovery ofhydrocarbons during waterfloods, with increased recovery resulting fromthe use of injection water of lower salinity than natural seawater butsufficient ionic strength to prevent clay instability. Depending on thetype of formation, injection fluids having higher salinity may cause thereservoir wettability to become more oilwet. This is because themultivalent cations in the brine, such as Ca⁺² and Mg⁺², are believed toact like bridges between the negatively charged oil and the negativelycharged clay minerals that typically line the pore walls of theformation. The oil reacts with the clay particles to form organometalliccomplexes, which results in the clay surface being extremely hydrophobicand oilwet. As the oilwetness of the reservoir rock increases,hydrocarbons will adsorb onto the surface of the rock and thereby flowless easily from the formation, relative to water, which results in lesshydrocarbon product being produced.

Lowering the electrolyte content (i.e., lowering the ionic strength) bylowering the overall salinity and especially reducing the concentrationof multivalent cations in the formation reduces the screening potentialof the cations. This results in increased electrostatic repulsionbetween the clay particles and the oil. Once the repulsive forces exceedthe binding forces via the multivalent cation bridges, the oil particlesare desorbed from the clay surfaces and the clay surfaces becomeincreasingly waterwet. If, however, the electrolyte content is reducedtoo much (i.e., the formation fluid salinity is too low), the clayparticles may be stripped from the pore walls (clay deflocculation),which will damage the formation. Thus, although it is desirable to havelower salinity injection water, it is important that the salinity levelsbe kept within a specified range.

Lower salinity water, however, is not often available at a well site.Lower salinity water is typically prepared, for example, by reducing thetotal ion concentration of higher salinity water using membraneseparation technology (e.g., reverse osmosis). In known seawaterdesalination plants operating according to the reverse osmosis process,the seawater to be desalinated is subjected to a separation process bymeans of a semi-permeable membrane. Such a membrane is understood to bea selective membrane, which is permeable to a high degree to the watermolecules, but only to a very low extent to the salt ions dissolvedtherein.

Membrane separation techniques used in the preparation of low salinityinjection water use reverse osmosis (RO) membrane elements. Membraneseparation techniques used in the preparation of low sulfate injectionwater and softened water use specialized nanofiltration (NF) membraneelements. The RO and NF processes use hydraulic pressure to producelower salinity water from feed water through a semipermeable membrane.Depending on the membrane type, pressure and water conditions, an amountof salt also passes across the membrane, but the overall salinity of theproduct water is less than that of the feed water. Current RO technologycan be used for desalinating both seawater and brackish water. Themembranes used in the RO process are generally either made frompolyamides or from cellulose sources.

The water to be treated is typically pretreated using cartridge filters,media filtration, microfiltration, or ultrafiltration methods, which areknown to separate solids/particulates from the water based on theirsize. The water is then fed to the reverse osmosis and/or nanofiltrationvessel using a high-pressure pump. The required pressure from thehigh-pressure pump is a function of the osmotic pressure, thetemperature, the flux (i.e., the rate at which the water passes througha unit area of the membrane), and the volume of the feed water to beproduced with a specific membrane area. The product water (i.e., thepermeate) is discharged from the membrane module by way of a permeateconduit. A concentrate conduit serves for discharging concentrated ionicwater.

Typically, conventional systems are only concerned with producing waterhaving certain characteristics in amounts higher or lower than apredetermined level. Such systems focus only on a maximum allowablelimit of a contaminant and treatment occurs as long as, and only if, theamount of the particular characteristic is above the set limit.Otherwise, the water is deemed acceptable for use. Most often, such atreatment plant will include several treatment blocks connected inseries and/or parallel. In such systems, water is passed through as manyof the multiple blocks, or through a particular block as many times, asis necessary for the particular characteristic in the water to reach theamount deemed acceptable for use.

SUMMARY

In one aspect, embodiments disclosed herein relate to a method fortreating seawater or other water sources for injection, the methodincluding intaking a first amount of water from a first source into aplurality of treatment blocks, treating the first amount of water,outputting aqueous treated water streams from each of the plurality oftreatment blocks, separating the aqueous treated water streams from eachof the plurality of treatment blocks into aqueous permeate streams andconcentrate reject streams, monitoring each of the aqueous permeatestreams, controlling the operation of at least one of the plurality oftreatment blocks based on predefined water-characteristic tolerancesthat fall within a predetermined concentration range based on thedifferent qualities of the aqueous permeate streams, outputting aproduct water stream into an injection water reservoir or blend point,the product water stream comprising the aqueous permeate stream,intaking a second amount of water from a second source into a producedwater reservoir, treating the second amount of water, and dischargingthe dischargeable water stream. Treating the first amount of waterincludes pumping at least a portion of the first amount of water throughthe plurality of treatment blocks. The monitoring includes identifyingdifferent characteristics of the aqueous permeate streams. Treating thesecond amount of water includes combining the second amount of waterwith the product water stream into a dischargeable water stream in theinjection water reservoir or at the blend point.

According to another aspect, there is provided a membrane-based watertreatment system, the system including a water intake system thatintakes a first amount of water, a plurality of treatment blocks, aproduced water reservoir that intakes a second amount of water; and aninjection water reservoir or blend point in fluid communication with theplurality of treatment blocks and the produced water reservoir. Each ofthe plurality of treatment blocks includes at least one pump, a membranepressure vessel, a monitor, and a controller. The pump feeds the firstamount of intake water through the membrane pressure vessel. Themembrane pressure vessel comprises at least one membrane element andseparates the first amount of intake water into at least an aqueouspermeate stream and a concentrate reject stream. The monitor is used toidentify different characteristics of each of the aqueous permeatestreams, monitor blending of the aqueous permeate streams from two ormore treatment blocks, and to monitor the blended aqueous permeatestreams from the two or more treatment blocks based on the identifiedcharacteristics and predefined water-characteristic tolerances.

Other aspects and advantages of the invention will be apparent from thefollowing description and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a prior art offshore production well.

FIG. 2 shows a seawater treatment process according to one or moreembodiments of the present invention.

FIG. 3A is a diagram of a seawater treatment unit on a vessel accordingto one or more embodiments of the present invention.

FIG. 3B is a diagram of a seawater treatment unit on an off-shore rigaccording to one or more embodiments of the present invention.

FIG. 3C is a diagram of a rig, a vessel, and a seawater treatment uniton the seafloor according to one or more embodiments of the presentinvention.

FIG. 4A shows another seawater treatment process according to one ormore embodiments of the present invention.

FIG. 4B shows a treatment block according to one or more embodiments ofthe present invention.

FIG. 4C shows a spiral wound membrane element according to one or moreembodiments of the present invention.

FIG. 4D shows a schematic for a hollow fine fiber membrane elementaccording to one or more embodiments of the present invention.

FIG. 4E shows another seawater treatment process according to one ormore embodiments of the present invention.

FIG. 5 shows an improved oil recovery system according to one or moreembodiments of the present invention.

FIG. 6A shows a configuration for a system or method according to one ormore embodiments of the present invention.

FIG. 6B shows a configuration for a system or method according to one ormore embodiments of the present invention.

FIG. 7 shows a configuration for a system or method according to one ormore embodiments of the present invention.

FIG. 8 shows another seawater treatment process according to one or moreembodiments of the present invention.

FIG. 9 shows another seawater treatment process according to one or moreembodiments of the present invention.

DETAILED DESCRIPTION

One or more embodiments of the present invention will be described belowwith reference to the figures. In one aspect, embodiments disclosedherein relate to systems and methods for treating seawater or otherwater source using customizable membrane technology to prepare anaqueous fluid having specific water characteristic tolerances that fallwithin predefined threshold values. In another aspect, embodimentsdisclosed herein relate to a water treatment process having acustomizable membrane system that may include a bypass blend line whichmay be used depending on the water outputted from the customizablemembrane system to achieve predefined threshold values. In yet anotheraspect, embodiments disclosed herein relate to the treatment of seawaterusing a customizable treatment system to produce an aqueous fluid whichhas specifically tailored properties and which is capable of being usedas an injection fluid to be used in improved oil recovery operations. Inyet another aspect, embodiments disclosed herein relate to blendingtreated fluids which have specifically tailored properties. In yetanother aspect, embodiments disclosed herein relate specifically toimproved oil recovery operations in offshore wells.

Seawater Treatment

Typically, seawater treatment systems are based on several factors. Mostimportantly, seawater treatment systems depend on the quality of theseawater (e.g., the temperature, salinity, and/or specific chemicalcomposition of the water). In particular, the input water temperaturevariance of the seawater is the most common factor that varies to whichthe treatment system must react in order to produce consistent waterquality. Water temperature impacts the treatment performance as afunction of the water and salt transport property variation of themembranes. Warmer water will result in treated water with highersalinity than the same treatment of cooler water. In addition, as themembrane used in the treatment system ages, its performance changes,thereby impacting the water and salt transport properties and theresulting treated water quality. According to embodiments of the presentinvention, depending on these factors, a treatment system may becustomized to produce any quality of output water desired.

As used herein, the term “predefined water-characteristic tolerances” isused to refer to the desired output water quality that falls withinpredefined threshold values for any system which will be using thetreated water. For example, in downhole applications, it may be desiredto produce a water having a salinity of between about 1,000 mg/L andabout 30,000 mg/L, a sulfate ion content of between about 5 mg/L and2,000 mg/L and hardness content of between 5 mg/L and 300 mg/L.

According to one or more embodiments of the present invention, aseawater treatment system may be used to produce water having predefinedwater-characteristic tolerances, for example, by controlling pumpswithin the system to ensure that any water having characteristicsoutside the predefined threshold values is appropriately blended eitherwith treated or untreated (or both) filtered water to produce a waterthat has characteristics falling inside the predefined threshold values.

In one embodiment, a treatment system comprising multiple membraneblocks may be modified so as to change the operation of each of themembrane blocks themselves so they produce different quality waterstreams based on the predefined water-characteristic tolerances. Thesedifferent quality water streams may then be blended together to form aproduct water stream having predefined water-characteristic tolerances.Alternatively, the product water stream may be further blended withuntreated filtered seawater from a blend/bypass line.

In particular, control devices may be used (e.g., a monitor and/ortransmitter) to modify or vary the operational parameters of each blockbased on the outputted permeate water streams. Operational parameters tobe modified may include input feed pressure, flux, temperature,flowrate, and water recovery.

Referring to FIGS. 2 and 3A-C, a seawater treatment system according toone or more embodiments is shown. As shown in FIG. 2, the presentinvention provides a seawater treatment system 200 that may include awater intake system 201, a membrane system 210, permeate transfer andtreatment system 220, a concentrate discharge system 230, a controlsystem 240, and a power source 290. Water intake system 201 may includewater intake(s) 202, water intake pump(s) 204, pre-filter(s) 206, andmembrane/media-filter(s) 208; membrane system 210 may include variablespeed high-pressure pump(s) 212, blend/bypass line(s) 225, either areverse osmosis and/or nanofiltration membrane(s) 214, andmonitor/transmitter(s) 226; the concentrate discharge system 230 mayinclude a plurality of discharge ports; and permeate transfer andtreatment system 220 may include permeate transfer pump(s) 222. While inthe exemplary embodiments shown, certain components may be shown by asingle block/symbol, those skilled in the art will appreciate that eachsystem described may be comprised of a plurality of such elements.

As shown in FIGS. 3A-C, the seawater treatment system 200 may beprovided on a vessel 300, on a rig 312, and/or on the seafloor 316.Alternatively, in one or more embodiments, the seawater treatment system200 may be used onshore.

Additionally, according to one or more embodiments, treatment block 260may be used to describe the system that includes, for example, membranesystem 210, blend/bypass line 225, concentrate discharge system 230.

The treatment block 260 is in communication with the water intake system201 and the permeate transfer and treatment system 220. Both the controlsystem 240 and the power source 290 are in communication with oneanother, as well as in communication with the water intake system 201,the permeate transfer and treatment system 220, and treatment block 260(i.e., membrane system 210 and concentrate discharge system 230). Asused herein, the terms “communicate” or “communication” mean tomechanically, electrically, or otherwise contact, couple, or connect bydirect, indirect, or operational means.

Within the water intake system 201, water intake pump 204 pumps theintake water through pre-filter 206 to remove any large contaminants(e.g., sand, rocks, plants, debris, etc.) and then through a lowpressure membrane or media filter 208 to remove large molecules (e.g.,suspended solids, colloids, macromolecules, bacteria, oils, particulatematter, proteins, high molecular weight solutes, etc.). One of ordinaryskill in the art will appreciate that depending on the specifications ofthe equipment and the type and density of particulate matter to beremoved, various types of filters, including for example, sand or mediafilters, cartridge filters, ultra filters, and/or micro filters may beused.

Furthermore, the water intake system 201 may include one or morevariable-depth extension members capable of extending into the body ofwater so as to intake water from a desired depth. Additionally, theextension member may include one or more intake screens designed to helpprevent fouling of the intakes by marine life or other particles. One ofordinary skill in the art will appreciate that depending on the intendedbody of water from which water is being taken, other equipment may alsobe employed.

After passing through water intake system 201, the filtered seawater maybe provided to blend/bypass line 225 and transferred directly topermeate treatment and transfer system 220 where it may then be combinedwith a permeate stream produced from membrane 214. Additionally, thefiltered seawater may be provided to treatment block 260 wherein avariable speed high-pressure pump 212 pushes the filtered seawaterthrough to membrane 214, whereby a concentrate is created on the highpressure side of the membrane 214 and a permeate stream is created onthe low pressure side of the membrane 214.

The permeate stream produced from membrane 214 may comprise predefinedwater-characteristic tolerances, i.e., water that has specific ionsand/or molecules removed therefrom, for example, the permeate stream mayhave lower sulfate ion content and/or lower salinity compared to thefiltered seawater produced from water intake system 201. The permeatestream may then be transferred, for example, from vessel 300 to rig 312,from seafloor 316 to rig 312, and/or from rig 312 to well 310, throughpermeate transfer and treatment system 220.

Alternatively, the permeate stream produced from membrane 214 may notcomprise the desired predefined water-characteristic tolerances and mayneed to be further treated in order to reach the predefinedwater-characteristic tolerances. For example, the permeate stream may beblended with other permeate streams and/or untreated filtered seawaterfrom the blend/bypass line. However, based on the quality of thepermeate stream produced from membrane 214, it may be necessary tochange the operation of the membrane block itself so it will produce adifferent quality water stream based on the outputted permeate streamproduced from the membrane and based on predefined water-characteristictolerances. Such a change may be made by using a monitor 226 to firstdetermine the quality of the outputted permeate stream and second tovary or change the operation of the membrane block itself (e.g., bycontrolling the pump 212 that pumps water into the membrane block 214and/or a concentrate line valve 223), thereby changing the quality ofthe outputted permeate stream for subsequent batches of water.

Additionally, permeate streams from various treatment blocks 260 may beblended together, and may be blended with untreated filtered seawaterfrom the blend/bypass line 225 to produce water having predefinedwater-characteristic tolerances. Each treatment block can use the sameor a different type of RO or NF membrane requiring its respectivepressure from the high-pressure pump 212. Blending the various permeatestreams from each treatment block can then provide a very specificcomposition of mono- and divalent ions as a function of optimumreservoir performance. According to one or more embodiments, this veryspecific composition may then be mixed with water from the blend/bypassline 225.

According to one or more embodiments of the present invention, a monitor226 may be used to detect the characteristics of the output permeatestreams. Based on these characteristics, one or more monitor 226 may beused to change the operation of the membrane block 214, for example, bycontrolling the variable speed high-pressure pump 212 in real-time tochange the amount of water being pumped through membrane 214, so as toproduce different quality water having predefined water-characteristictolerances. Additionally, based on these characteristics, untreatedfiltered seawater from the blend/bypass line 225 may be blended in withthe output permeate streams in order to achieve a water having even morespecific water-characteristics tolerances.

In one or more embodiments, a permeate stream from a treatment block 260can be further treated using forward osmosis (FO) or other treatment,which impacts the chemical composition of the water to further refinethe ionic balance as a function of achieving optimum reservoirperformance.

In one or more embodiments, instead of seawater as the source of waterthrough intake system 201, brackish water or produced water could be thefeed water, thereby allowing the flexibility to switch between brackishwater, produced water, and seawater treatment.

The permeate transfer and treatment system 220 may be capable oftransferring the permeate produced to a permeate delivery systemcomprising a pipeline in communication with the permeate transfer andtreatment system 220. The pipeline may transfer the permeate, forexample, from vessel 300 to rig 312, from seafloor 316 to rig 312,and/or from rig 312 to well 310. The permeate transfer and treatmentsystem 220 may also be capable of treating the permeate produced eitherprior to, during, or after the permeate is transferred. Treatment of thepermeate may include “post-treatment,” for example, chemical addition(e.g., in line chemical injection) and/or deaeration (e.g., in a vacuumsystem).

The concentrate created on the high pressure side of the membrane 214comprises the ions and/or molecules removed by membrane 214. Theconcentrate is then disposed of, for example, through a plurality ofconcentrate discharge ports within the concentrate discharge system 230.However, before the concentrate is disposed of, an energy recoverydevice (not shown) may be used to capture the energy possessed by theconcentrate and return such energy to the variable speed high-pressurepump 212.

Furthermore, the concentrate may be diluted or otherwise treated priorto disposal. For example, in one or more embodiments, the concentratedischarge system 230 may be configured to increase the mixing of theconcentrate discharged into the surrounding body of water. The pluralityof discharge ports of the concentrate discharge system 230 may bephysically located above or below the water line 318 of the vessel 300and/or the rig 312. Also, the discharge ports may be disposed on avariable-depth extension member that can be positioned so as to promotedispersion of the concentrate into the body of water.

in one or more embodiments, the effluent from membrane 214 (either thepermeate stream or the concentrate) may take one or more subsequentpasses through membrane 214 and concentrate streams may be recycled toearlier positions in the treatment scheme.

According to one or more embodiments of the present invention, separatepower source(s) may provide power to each of the water intake system201, permeate transfer and treatment system 220, treatment block 260(i.e., membrane system 210 concentrate discharge system 230), monitor226, and propulsion device 302. For example, each of the water intakepump 204, variable speed high-pressure pump 212, monitor 226, andpermeate transfer pump 222 may be in communication with a separate powersource.

According to one or more embodiments, the seawater treatment system 200may be land-based or provided on a vessel. Where the seawater treatmentsystem 200 is provided on a vessel 300, vessel 300 may further comprisea propulsion device 302 in communication with the power source 290. Thevessel 300 may be a self-propelled ship, a moored, towed, pushed orintegrated barge, or a flotilla or fleet of such vessels. The vessel 300may be manned or unmanned. The vessel 300 may be either a single-hull ordouble-hull vessel.

Alternatively, in one or more embodiments, a single power source mayprovide power to a combination of two or more of the water intake system201, membrane system 210, permeate transfer and treatment system 220,concentrate discharge system 230, monitor 226, and/or propulsion device302 where the seawater treatment system 200 is provided on a vessel 300.For example, electric power for the variable speed high-pressure pump212 may be provided by a generator driven by the power source for thevessel's propulsion device, such as a vessel's main engine. In such anembodiment, a step-up gear power take off or transmission would beinstalled between the main engine and the generator in order to obtainthe required synchronous speed.

Further, an additional coupling between the propulsion device and themain engine allows the main engine to drive the generator while thevessel is not under way. Moreover, an independent power source (notshown), such as a diesel, steam, or gas turbine, renewable energygenerator, or combinations thereof, may power the treatment block 260,the propulsion device 302, or both.

In other embodiments, the power source for seawater treatment system 200may be dedicated solely to the seawater treatment system 200.

In one or more embodiments, the plurality of concentrate discharge portsof the concentrate discharge system 230 may act as an auxiliarypropulsion device for the vessel 300 or act as the sole propulsiondevice for the vessel 300. Some or all of the concentrate may be passedto propulsion thrusters to provide idling or emergency propulsion.

In one or more embodiments, the power source 290 may compriseelectricity producing windmills and/or water propellers that harness theflow of the air and/or water to generate power for the seawatertreatment system 200 and/or the operation of the vessel 300 and/or rig312.

For embodiments where the seawater treatment system 200 is on a vessel300, the water intake system 201 may be capable of taking in seawaterfrom the water surrounding the vessel 300 and providing it to thetreatment block 260. In such embodiments, the water intake 202 of thewater intake system 201 may include one or more apertures in the hull ofthe vessel 300 below the water line 318. An example of a water intake202 is a sea chest (not shown). Water is taken into the vessel 300through the one or more apertures (i.e., water intake 202), passedthrough the water intake pump 204, pre-filter 206, membrane/media filter208, and either supplied to the variable speed high-pressure pump 212 orsupplied to the blend/bypass line 225, or both.

For embodiments where the seawater treatment system 200 is on anoffshore rig 312, the water intake system 201 may be capable of takingin seawater from the water surrounding the rig 312 and providing theseawater to the treatment block 260. In such embodiments, the waterintake 202 of the water intake system 201 may include an intakeriser(s), screen(s), and external or submerged pump(s).

For embodiments where the seawater treatment system 200 is on theseafloor 316, the water intake system 201 may be capable of taking inseawater from the water surrounding the seawater treatment system 200and providing it to the membrane system 210. In such embodiments, thewater intake 202 of the water intake system 201 may include an intakewell or riser, screen(s) and pump(s).

The membrane system 210 may comprise a variable speed high-pressure pump212, a membrane 214, a blend/bypass line 225, and a monitor 226.

In one or more embodiments, membrane 214 is an ion selective membrane,which may selectively prevent or at least reduce hardening orscale-forming ions (e.g., divalent ions including sulfate, calcium, andmagnesium ions) from passing across it, while allowing water and otherspecific ions (e.g., monovalent ions including sodium, chloride,bicarbonate, and potassium ions) to pass across it. The selectivity ofthe membrane may be a function of the particular properties of themembrane, including pore size and charge characteristics of thepolymeric structure comprising the membrane. For example, a polyamidemembrane, a cellulose acetate membrane, a nano-embedded membrane, apiperazine-derivative membrane and/or other membrane innovation may beused to selectively prevent or at least reduce sulfate, calcium, andmagnesium ions from passing across it. In one or more embodiments,membrane 214 may reduce up to about 99% of the sulfate ions.

In one or more embodiments, membrane 214 is a desalting membrane, whichmay lower the total salinity or ionic strength of the filtered seawaterby preventing or at least reducing ions (e.g., sodium, chloride,calcium, potassium, sulfate, bicarbonate, and magnesium ions) frompassing across it.

In one or more embodiments, membrane 214 is a nanofiltration membrane.Examples of commercially available nanofiltration membranes suitable foruse in the treatment process of the present disclosure may include, forexample, FILMTEC™ SR90 Series, NF 200 Series, NF90 Series which isavailable from The Dow Chemical Company (Minneapolis, Minn.), ormembranes with similar rejection properties from other membranemanufacturers.

In one or more embodiments, membrane 214 is a reverse osmosis membrane.Examples of commercially available reverse osmosis membranes suitablefor use in the treatment process of the present disclosure may include,for example, FILMTEC™ SW 30 Series, which is available from The DowChemical Company (Minneapolis, Minn.), or other membranes with similarrejection properties from other membrane manufacturers.

As shown in FIGS. 4A-B, the seawater treatment system 200 may include amembrane system 210 that includes a plurality of membrane pressurevessels (shown as 214, 216, and 218), which may be arranged in parallel.Although three membrane pressure vessels are shown, other embodimentsmay include more or less than three membranes. According to one or moreembodiments, each membrane pressure vessel 214, 216, 218, may include aplurality of membrane elements 250 installed therein. Although sixelements 250 are shown in each membrane pressure vessel, otherembodiments may include more or less than six elements 250.

Further, in one or more embodiments, at least one of each of aconductivity sensor 224, a flow sensor 226, and a hardness sensor 227may be disposed on the blend/bypass line 225. In one or moreembodiments, each of the conductivity sensor 224, the flow sensor 226,and the hardness sensor 227 may be disposed on the blend/bypass line 225to measure conductivity, flow, and hardness of water, respectively,passing through the blend/bypass line 225 on each permeate of themembrane pressure vessel. For example, as shown in FIG. 4A, each of theconductivity sensor 224, the flow sensor 226, and the hardness sensor227 may be disposed on the blend/bypass line 225 to measureconductivity, flow, and hardness of water, respectively, in theblend/bypass line 225 after the water passes through each membranepressure vessel 214, 216, 218. Those having ordinary skill in the artwill appreciate that each of the conductivity sensor 224, a flow sensor226, and a hardness sensor 227 may be any conductivity sensor, flowsensor, or hardness sensor known in the art.

Furthermore, in one or more embodiments, the seawater treatment system200 may include a desalination water controller 265. In one or moreembodiments, the desalination water controller 265 may take signals fromdesalination plant sensors and output signals to the main plant 240.

As shown in FIGS. 4B-C, according to one or more embodiments, eachelement 250 may comprise, for example, reverse osmosis membraneelements, nanofiltration membrane elements, or other membrane elementsknown in the art. Membrane elements 250 may comprise one of severalconfigurations known in the art, for example, spiral wound (SW) and/orhollow fine fiber (HFF).

As shown in FIG. 4C, according to one or more embodiments, elements 250may comprise spiral wound elements 250. Spiral wound elements 250 may beconstructed from flat sheet membranes 254 and 256 and may include abacking material 258 to provide mechanical strength. The membranematerial may be cellulosic (i.e., cellulose acetate membrane) ornon-cellulosic (i.e., composite membrane). For cellulose acetatemembranes, the two layers may be different forms of the same polymer,referred to as “asymmetric.” For composite membranes, the two layers maybe completely different polymers, with the porous substrate often beingpolysulfone.

In the spiral wound design, the membrane is formed in an envelope thatis sealed on three sides. A supporting grid, called the product watercarrier, is on the inside. The envelope is wrapped around a centralcollecting tube 261, with the open side sealed to the tube. Severalenvelopes, or leaves, are attached with an open work spacer material 262between the leaves. This is the feed/concentrate, or feed-side spacer.The leaves are wound around the product water tube 261, forming spiralsif viewed in cross section. Each end of the unit may be finished with aplastic molding, called an “anti-telescoping device,” and the entireassembly may be encased in a thin fiberglass shell (not shown). Feedwater may flow through the spiral over the membrane surfaces, roughlyparallel to the product water tube 261. Product water flows in a spiralpath within the envelope to the central product water tube 261. Achevron ring (not shown) around the outside of the fiberglass shell mayforce the feed water to flow through the element 250.

As shown in FIG. 4D, according to one or more embodiments, elements 250may comprise hollow fine fiber elements 270. The design of the hollowfine fiber elements 270 may include a plurality of hollow fibermembranes 272 being placed in a membrane pressure vessel 280. The hollowfine fiber may be a polyaramid or a blend of cellulose acetates. Themembranes 272 may have an outside diameter of about 100 to about 300microns and in inside diameter between 50 and about 150 microns. Thefibers may be looped in a U-shape, so both ends are imbedded in aplastic tubesheet 274. The pressurized seawater may be introduced intothe vessel (indicated by arrow 276) along the outside of the hollowfibers. Under pressure, desalted water passes through the walls of thehollow fiber membranes 272 and flows down the inside of the fibermembranes 272 to a permeate collection tube 278 for collection (asindicated by arrow 282), while the separated concentrate is removed fromthe membrane pressure vessel 280 (as indicated by arrow 284).

According to one or more embodiments, all of the membrane pressurevessels in membrane system 210 may comprise elements 250 having onlyreverse osmosis membrane elements installed therein. In anotherembodiment, all of the membrane pressure vessels in membrane system 210may comprise elements 250 having only nanofiltration membrane elementsinstalled therein. In other embodiments, one or more membrane pressurevessel (e.g., membrane pressure vessel 214) may comprise elements 250having either nanofiltration or reverse osmosis membrane elementsinstalled therein while the remaining membrane pressure vessels (e.g.,membrane pressure vessels 216 and 218) comprise elements 250 having onlyreverse osmosis or nanofiltration membrane elements installed therein.While specific examples of combinations of membrane pressure vessels andmembrane element types are listed here, these examples are not intendedto be exhaustive and other combinations may be used. Those skilled inthe art will appreciate other appropriate examples and combinations,which are intended to be encompassed by one or more embodiments.

As shown in FIGS. 3A-C, one or more treatment blocks 260 may beinstalled on the deck 304 of a vessel 300, on the platform 305 of a rig312, and/or on the seafloor 316, depending on the location of theseawater treatment system 200. Additionally, the one or more treatmentblocks may also be installed in other parts of the vessel 300 and/or therig 312, or even on multiple levels of the vessel 300 and/or the rig312. For example, each treatment block may be installed in a separatecontainer. Several containers can be placed on top of each other tooptimize the use of the deck 304 and/or platform 305 to decrease thetime and expense associated with construction of the seawater treatmentsystem on the vessel 300 and/or rig 312. The one or more treatmentblocks may be installed in series or in parallel.

Within the water intake system 201, water intake pump 204 pumps theintake water through pre-filter 206 to remove any large contaminants(e.g., sand, rocks, plants, debris, etc.) and then through filter 208 toremove large molecules (e.g., suspended solids, colloids,macromolecules, bacteria, oils, particulate matter, proteins, highmolecular weight solutes, etc.). After passing through water intakesystem 201, the filtered seawater is provided to treatment block 260 byvariable speed high-pressure pump 212. Although only one treatment block260 is shown, according to one or more embodiments, there may be morethan one treatment block arranged in series and/or in parallel.

According to one or more embodiments, within treatment block 260, theremay be one or more membrane pressure vessels (e.g., 214, 216, and 218).In one embodiment, the pressurized seawater may be pushed through thefirst membrane pressure vessel (e.g., 214) having one or more elements250 with membrane elements installed therein, thereby creating a firstpermeate stream and a first concentrate stream. The first permeatestream may comprise water that has specific ions removed therefrom, forexample, the first permeate stream may have lower sulfate ion contentand/or lower salinity compared to the filtered seawater produced fromwater intake system 201. The first concentrate stream may comprise theions and/or molecules removed by the membrane elements in the firstmembrane pressure vessel (e.g., 214). The first concentrate stream maythen be disposed of, for example, through a plurality of concentratedischarge ports within the concentrate discharge system 230. However,before the first concentrate is disposed of, an energy recovery device(not shown) may be used to capture the energy possessed by the firstconcentrate stream and return such energy to the variable speedhigh-pressure pump 212.

According to one or more embodiments, one or more monitors 226 may beused to determine the characteristics of the output permeate streamscreated by the one or more membrane pressure vessels 214, 216, 218.According to one or more embodiments, one or more monitors 226 may beused to determine the characteristics of the streams created by blendingthe output permeate streams with the blend/bypass lines. Based on thesecharacteristics, monitors 226 may be used to change the performance ofthe membranes in pressure vessels 214, 216, 218 to produce differentquality water by controlling the variable speed high-pressure pumps 212to change, real-time, the amount of water being pumped through membranepressure vessels 214, 216, 218. Similarly, based on thesecharacteristics, monitors 226 may be used to control the amount ofuntreated filtered seawater water provided to the blend/bypass line 225,i.e., monitors 226 may be used to trigger an amount of untreatedfiltered seawater water being blended in with the output permeatestreams in order to achieve a water having even more specificcharacteristics.

According to one or more embodiments, this process may continue for asmany membrane pressure vessels as there are in the treatment block 260.Additionally, this process may continue for as many treatment blocks 260as there are in the treatment system 200, until a final permeate stream,optionally having untreated filtered seawater water blended therein, isproduced from a final membrane pressure vessel. The final permeatestream may then be transferred, for example, from vessel 300 to rig 312,from seafloor 316 to rig 312, and/or from rig 312 to well 310, throughthe permeate transfer and treatment system 220.

In one or more embodiments, the membrane elements installed within themembrane pressure vessels (e.g., 214, 216, and 218) are all ionselective membrane elements that lower the salinity or ionic strength ofthe seawater by selectively preventing or at least reducing certain ions(e.g., sodium, calcium, potassium, and magnesium ions) from passingthrough the membrane elements, while allowing water and other specificions (e.g., sulfate, calcium, magnesium, and bicarbonate ions) to beproduced for use and/or further treatment. In other embodiments, themembranes elements are all ion selective membranes that selectivelyprevent or at least reduce hardening or scale-forming ions (e.g.,sulfate, calcium, magnesium, and bicarbonate ions) from passing throughthe membrane elements, while allowing water and other specific ions(e.g., sodium and potassium ions) to be produced for use and/or furthertreatment.

In one or more embodiments, the seawater treatment system 200 mayinclude multiple treatment blocks 260, wherein the multiple treatmentblocks 260 each comprise different membrane pressure vessels. Forexample, in one embodiment, one or more treatment block 260 may includemembrane pressure vessels (e.g., 214, 216, and 218) having membraneelements installed therein wherein the membrane elements comprise onlynanofiltration membrane elements, while one or more separate treatmentblock 260 includes membrane pressure vessels (e.g., 214, 216, and 218)having membrane elements installed therein wherein the membrane elementscomprise only reverse osmosis membrane elements. Additionally, one ofordinary skill in the art would recognize that the number of treatmentblocks in a system may vary in one or more embodiments. Further, one ofordinary skill in the art in possession of the present disclosure willrecognize that the membrane elements may vary and may be, for example,spirally wound, hollow fiber, tubular, plate and frame, or disc-type.

According to one or more embodiments, the variable speed high-pressurepump that operates to push the pretreated water through the treatmentblock 260 may be controlled by monitor 226 and may comprise any pumpsuitable to generate the hydraulic pressure necessary to push the waterthrough the one or more membrane pressure vessels. However, the pumpdischarge pressure must be controlled in order to maintain thedesignated permeate flow and, more importantly, to not exceed themaximum allowed feed pressure for the membrane elements being used. Thisis of particular importance because if the maximum allowed feed pressureis exceeded, the membrane element may blow out and thereby failprematurely. Because the maximum allowed feed pressure fornanofiltration elements is typically much less than the maximum allowedfeed pressure for reverse osmosis element, conventional membrane systemshaving more than one type of membrane (e.g., nanofiltration and reverseosmosis) typically require more than one pump (i.e., a pump for eachtype of membrane). Conventional systems with nanofiltration membranesinstalled cannot change to reverse osmosis membranes due to thispressure differential.

However, according to one or more embodiments, the treatment block 260may include a variable-speed high-pressure pump 212 that is controlledby monitor 226 and that provides the filtered seawater to more than onemembrane pressure vessel. Because the membrane pressure vessels may varyin size and/or may include different types of membrane elements, andtherefore require varying feed pressures, the high-pressure pump 212must be able to provide an adjustable feed pressure based on the type ofsystem being used and based on the water characteristics detected by themonitor 226. In one or more embodiments, the variable speedhigh-pressure pump may comprise, for example, a positive displacementpump.

In one or more embodiments, a pump may be used to provide approximately16,068 m³/d (or 670 m³/hr or 2950 gpm) at varying pressures.Specifically, for a seawater reverse osmosis (SWRO) treatment systemwith an energy recovery device (ERD), the lowest needed pressure isabout 26.5 bar and the highest needed pressure may be about 30.2 bar.For an NF system with no ERD, the lower required pressure is about 27bar while the highest required pressure may be about 39 bar. For asulfate reducing nanofiltration (SRNF) system with no ERD, the lowestneeded pressure may be about 14 bar and the highest required pressuremay be about 19 bar.

One or more embodiments of the present invention may also includevariable frequency drives (VFD) on the high-pressure pump. The VFD aresystems that control the rotational speed of an alternating current (AC)electric motor by controlling the frequency of the electrical powersupplied to the motor. By employing VFD, the pressures created by thevariable speed high-pressure pump can also be varied according to thespecific needs of the system at any time, for example, as a function ofoperation, membrane type, water quality objectives, and/or seawatertemperature and salinity.

Referring to FIG. 4E, in one or more embodiments, a slip stream line 295may be included in the system. Like elements of the system shown in FIG.4E to the elements shown and described in other embodiments are givenlike reference numerals and detailed description thereof is omitted. Inembodiments including a slip stream line 295, the controller 265 mayalso control valves 296 connecting the slip stream line 295 to otherlines in the system for addition of specially-treated water. The valves296 may be located at various positions in the system, e.g., at theentrances of the system pumps, at water blending points in the system,etc. For instance, the slip stream line 295 may contain water having anadditive acid or base to assist with balancing the quality of the waterbeing processed. Additionally, the slip stream line may contain warmeror cooler water than the water in the system to assist with balancingthe temperature of the water being processed. Controller 265 may blendwater from slip stream 295 so as to improve overall system efficiency,reduce power consumption, etc.

Accordingly, one or more embodiments provide a seawater treatment systemhaving the flexibility to switch between multiple membrane elementsusing high-pressure pumps that may be varied, real-time, by a controllerthat monitors the characteristics of the output permeate streams andthen transmits a signal to the high-pressure pumps to either pump moreor less water through the membrane elements and/or blend in untreatedfiltered seawater from the blend/bypass line to achieve a water havingspecifically tailored properties without having to pass through multipletreatment systems. For example, as shown in FIGS. 4A-4B, VFDs 212A maybe integrated into the seawater treatment system 200 and may allow thepressures created by the high-pressure pumps 212 to be varied accordingto the specific needs of the seawater treatment system 200 at any time.

As discussed above, seawater has a high ionic content relative to freshwater. For example, seawater is typically rich in ions such as sodium,chloride, sulfate, magnesium, potassium, and calcium ions. Seawatertypically has a total dissolved solids (TDS) content of at least about30,000 mg/L. According to one or more embodiments, it is preferred thatthe permeate stream have a total dissolved solids content of betweenabout 1,000 mg/L and about 30,000 mg/L.

Improved Oil Recovery

As noted above, improved oil recovery processes commonly inject waterinto a subterranean hydrocarbon-bearing reservoir via one or moreinjection wells to facilitate the recovery of hydrocarbons from thereservoir via one or more hydrocarbon production wells. The water can beinjected into the reservoir as a waterflood in a secondary oil recoveryprocess. Alternatively, the water can be injected into the reservoir incombination with other components as a miscible or immiscibledisplacement fluid in a tertiary oil recovery process. Water is alsofrequently injected into subterranean oil and/or gas reservoirs tomaintain reservoir pressure, which facilitates the recovery ofhydrocarbons and/or gas from the reservoir.

According to one or more embodiments, injection fluids may includeaqueous solutions (e.g., seawater) that have been treated according tomethods disclosed above. In a particular embodiment, the seawater mayfirst undergo filtration in a water intake system whereby the seawateris pumped through a first filter to remove any large contaminants (e.g.,sand, rocks, plants, debris, etc.) and then through a second filter toremove large molecules (e.g., suspended solids, colloids,macromolecules, bacteria, oils, particulate matter, proteins, highmolecular weight solutes, etc.). One of ordinary skill in the art willappreciate that depending on the specifications of the equipment and thetype and density of particulate matter to be removed, various types offilters, including for example, sand or media filters, cartridgefilters, ultra filters, and/or micro filters may be used.

After passing through the water intake system, the filtered seawater maybe provided to a seawater treatment system such as the one depicted inthe figures of the present disclosure. Specifically, as shown in FIGS.4A-B, the filtered seawater may be provided to a treatment block 260 andeither sent through blend/bypass line 225 or pumped by variable speedhigh-pressure pump 212, which pushes the filtered seawater through toone or more membrane pressure vessels (e.g., 214, 216, and 218), therebycreating a permeate stream and a concentrate stream.

The permeate stream may comprise water that has specific ions and/ormolecules removed therefrom, for example, the permeate stream may havelower sulfate ion content and/or lower salinity compared to the filteredseawater produced from the water intake system. A monitor may be used todetect the characteristics of the permeate stream and, based on thesecharacteristics, control the high-pressure pumps and blend line andeffectively produce a water that is customized for a very specificpurpose. As shown in FIG. 5, the permeate stream may then betransferred, for example, from vessel 300 to rig 512, from seafloor 516to rig 512, and/or from rig 512 to well 510, through permeate transfersystem 520 and used as an injection fluid for improved recovery ofhydrocarbons from a subterranean hydrocarbon-bearing formation 514.

The concentrate stream may comprise the ions and/or molecules removed bythe membrane elements within the one or more membrane pressure vessels.The concentrate stream may then be disposed of, for example, through aplurality of concentrate discharge ports within the concentratedischarge system. However, before the concentrate is disposed of, anenergy recovery device may be used to capture the energy possessed bythe concentrate stream and return such energy to variable speedhigh-pressure pump. Also, the concentrate may be diluted or otherwisetreated prior to disposal.

In one or more embodiments, the effluent from the one or more membranepressure vessels (either the permeate stream and/or the concentratestream) may take one or more subsequent passes through treatment block260. Additionally, in some embodiments, more than one treatment blockand/or more than one blend/bypass line may be used in the seawatertreatment system.

In one or more embodiments, a method for recovering hydrocarbons from asubterranean hydrocarbon-bearing formation 514 may include injecting thepermeate stream into a hydrocarbon-bearing formation 514 via aninjection well 560, displacing hydrocarbons with the permeate towards anassociated hydrocarbon production well 580, and recovering thehydrocarbons from the formation 514 via the hydrocarbon production well580.

Preferably, the methods of one or more embodiments may result in anincrease in hydrocarbon recovery from a hydrocarbon bearing formation,for example in the range of about 2% to about 40%, when compared with awaterflood treatment using untreated high salinity injection water.

As shown in FIGS. 6A-B, the systems and methods of one or moreembodiments of the present invention may be included in variousconfigurations. Specifically, as shown in FIGS. 6A-B, a system and/ormethod of the present invention may be configured so that the variablespeed high-pressure pump 212 pushes the filtered seawater 611 throughone or more treatment blocks, thereby creating a concentrate stream 634and a permeate stream (not shown), wherein the permeate stream may thenbe analyzed using a monitor (not shown) to determine the characteristicsof the output permeate stream. Based on these characteristics, themonitor may be used to control the variable speed high-pressure pump 212real-time by varying the amount of water being pumped through membrane214. Additionally, based on these characteristics, untreated filteredseawater from the blend/bypass line 225 may be blended in with thepermeate stream in order to achieve a water having specificcharacteristics.

The concentrate stream 634 may then be disposed of, for example, througha plurality of concentrate discharge ports within the concentratedischarge system. However, before the concentrate stream 634 is disposedof, an energy recovery device 232 may be used to capture the energypossessed by the concentrate stream 634 and return such energy tovariable speed high-pressure pump 212. Also, the concentrate stream 634may be diluted or otherwise treated prior to disposal. Alternatively, asshown in FIG. 6B, a system and/or method of the present invention may beconfigured so that the concentrate stream 634 bypasses the concentratedischarge system, for example, via elbow piping 613.

Additionally, in other embodiments of the present invention, the systemsand/or methods of the present invention may be capable of switching backand forth between systems shown in FIGS. 6A-B. For example, whenblending of untreated filtered seawater with the permeate streams isdesired, the monitor may be used to control the variable speedhigh-pressure pump so as to pump an appropriate amount of water throughone or more treatment blocks and produce one or more permeate streamswhich may then be blended with untreated filtered seawater from theblend/bypass line; however, when blending of untreated filtered seawateris not required, the blend/bypass line may be bypassed.

Furthermore, as shown in FIG. 7, a system and/or method according to oneor more embodiments of the present invention may include both an energyrecover device 232 and elbow piping 613, wherein the energy recoverdevice 232 and the elbow piping 613 are connected via valves 614. In oneembodiment, the valves 614 may be left open so as to allow theconcentrate stream 634 to be piped directly in to the energy recoverdevice 232. In another embodiment, some valves 614 may be closed so asto bypass the energy recover device 232. Also, the concentrate stream634 may be diluted or otherwise treated prior to disposal.

EXAMPLES

The following examples are provided to further illustrate theapplication and use of the methods and systems disclosed herein fortreating seawater.

Example 1

A system comprised of a treatment block of seawater reverse osmosismembranes and a treatment block of seawater nanofiltration membranes isconfigured such that the flowrates to each treatment block and therespective high-pressure pump to each block can be regulated. Thetreatment block is comprised such that it produces approximately 60% ofthe permeate flow using the nanofiltration block operating at 42%recovery and 40% of the permeate flow using the reverse osmosis blockoperating at 40% recovery. In this example, the specific (target)salinity (total dissolved solids) of the blended permeate is 2,900 mg/L(+/−100 mg/L) and the maximum allowable hardness is 60 mg/L (as definedby the combined calcium and hardness ion concentration, in mg/L). Theoperating range of the system is 25 to 30° C.

Exhibit 1 provides the natural deviation of the salinity and hardness ofa conventional system, comprised of 60% nanofiltration and 40% reverseosmosis, over the temperature range.

Exhibit 1 Conventional Permeate Flow Membrane System Distribution Flux,Lmh TDS, mg/L Hardness NF RO NF RO 25 2918 51.1 60% 40% 14.57 14.50 303723 67.2 60% 40% 14.57 14.50

The results indicate that the permeate at 25° C. meets the permeatewater quality specifications but the permeate produced at 30° C. doesnot.

If the feed flows are reapportioned between the two treatment blockssuch that 49% of the permeate flow originates from the nanofiltrationblock and 51% originates from the reverse osmosis block, withcorresponding changes in membrane flux and feed pressures, then theblended permeate quality will meet the water quality specifications at30° C., as shown in Exhibit 2.

Exhibit 2 Conventional Permeate Flow Membrane System Distribution Flux,Lmh TDS, mg/L Hardness NF RO NF RO 25 2918 51.1 60% 40% 14.57 14.50 302905 51.7 49% 51% 15.76 18.50

In Exhibit 2, approximately 25% of the NF membranes were removed fromservice due to lack of need, through the use of automated valve.

Example 2

A system comprised of a treatment block of seawater reverse osmosismembranes and a by-pass stream treatment block of seawaternanofiltration membranes is configured such that the flowrates to eachtreatment block and the respective high-pressure pump to each block canbe regulated. The treatment block is comprised such that it producesapproximately 92.8% of the permeate flow using the seawater reverseosmosis membrane block operating at 45% recovery and the remainingpermeate flow using a slipstream of permeate from a multi-passnanofiltration membrane block operating at 75%, 80% and 80% recovery,respectively, for the three-pass system. In this example, the specific(target) salinity (total dissolved solids) of the blended permeate is2,000 mg/L (+/−50 mg/L) and the maximum allowable calcium is 10 mg/L,the maximum allowable magnesium is 10 mg/L, and the maximum allowablesulfate is 10 mg/L. The operating range of the system is 22 to 31° C.

Exhibit 3 provides the natural deviation of the salinity, calcium,magnesium and sulfate over the temperature range.

Exhibit 3 System with Conventional Operation Permeate Flow Mg²⁺,Distribution TDS, mg/L Ca²⁺, mg/L mg/L SO₄ ²⁻ SWRO 3-pass NF 22 1872 1.02.8 2.3 92.9% 7.1% 25 2016 1.4 3.3 2.7 31 2183 2.0 4.6 3.7

The results indicate that the permeate produced at 25° C. meets thepermeate water quality specifications but the permeate produced outsidethis design point does not meet the salinity requirement.

If the high salinity, low hardness, low sulfate slipstream is used toadjust the salinity across the operating seawater temperature range,then the blended permeate salinity can be controlled within the setpointof 2,000 mg/L, as shown in Exhibit 4.

Exhibit 4 System with Conventional Operation Permeate Flow Mg²⁺,Distribution TDS, mg/L Ca²⁺, mg/L mg/L SO₄ ²⁻ SWRO 3-pass NF 22 2005 1.12.8 2.3 92.3% 7.7% 25 2016 1.4 3.3 2.7 92.9% 7.1% 31 2017 1.9 4.6 3.893.6% 6.4%

For a 100,000 bbl/day (15,898 m³/day) injection system, the flowrate ofthe RO system will vary between 92,300 and 93,600 bbl/day (14,674 and14,481 m³/day) and the NF slipstream requirements will vary between7,700 and 6,400 bbd/day (1,224 and 1,017 m³/day). The control systemwill adjust the required flows from the respective systems to meet theconductivity setpoint and any excess water can be disposed to sea (dueto its high quality) or alternatively, the production of the two systemscan be dialed up or turn as needed, noting the resulting change in flux.

Additionally, while the above embodiments were described as beingapplication for offshore water treatment, one of ordinary skill in theart would appreciate that the treatment techniques may also be used inland-based operations, particularly when the feed water has a highsalinity and/or high ionic content.

Furthermore, one skilled in the art in possession of this specificationwill appreciate that the system and method are also applicable to otherwater treatment environments. For example, by substituting one or moretreatment blocks as appropriate, municipalities could use the system andmethod to produce portable or otherwise treated water.

Another aspect of the present disclosure is directed to a method fortreating water. The method for treating water may include intaking afirst amount of water into a plurality of treatment blocks and treatingthe first amount of water. In one or more embodiments, treating thefirst amount of water may include pumping at least a portion of thefirst amount of water through the plurality of treatment blocks. Themethod may also include outputting aqueous treated water streams fromeach of the plurality of treatment blocks, separating the aqueoustreated water streams from each of the plurality of treatment blocksinto aqueous permeate streams and concentrate reject streams, monitoringeach of the concentrate and permeate streams, in which the monitoringincludes identifying different characteristics of the streams. Further,the method may also include controlling the operation of at least one ofthe plurality of treatment blocks based on predefinedwater-characteristic tolerances that fall within a predeterminedconcentration range based on the different qualities of the streams,outputting a product water stream, and re-treating the product waterstream, in which re-treating includes pumping at least a portion of theproduct water stream through the plurality of treatment blocks. In oneor more embodiments, the product water stream may include the permeatestream, the concentrate stream, or a combination of permeate streams andconcentrate streams utilizing different membrane products.

Referring now to FIG. 8, one or more embodiments of the presentdisclosure are directed to a membrane-based water treatment system 200.In one or more embodiments, the water treatment system may include awater intake system (e.g., the main plant 240) that intakes a firstamount of water, a plurality of treatment blocks (214, 216, and 218),which may be arranged in parallel, a concentrate discharge system 230configured to discharge the concentrate reject stream, and a concentratere-blending unit 285 and may be configured to monitor thecharacteristics of a concentrate reject stream and selectively re-blendthe concentrate reject stream back through the water intake system. Asdiscussed above, although three membrane pressure vessels are shown,other embodiments may include more or less than three membranes.According to one or more embodiments, each membrane pressure vessel 214,216, 218, may include a plurality of membrane elements 250 installedtherein. Although six elements 250 are shown in each membrane pressurevessel, other embodiments may include more or less than six elements250.

In one or more embodiments, the plurality of treatment blocks mayinclude a pump 204, a membrane pressure vessel (shown as 214, 216, and218), a monitor 226, and a controller 265. In one or more embodiments,the pump may feed the first amount of intake water through the membranepressure vessel, the membrane pressure vessel may include at least onemembrane element and separates the first amount of intake water into atleast an aqueous permeate stream and a concentrate reject stream.Further, the monitor may be used to identify different characteristicsof each of the aqueous permeate streams and the concentrate rejectstream, monitor blending of the concentrate reject streams from two ormore treatment blocks, and to monitor the blended concentrate rejectstreams from the two or more treatment blocks based on the identifiedcharacteristics and predefined water-characteristic tolerances.

As discussed above, in one or more embodiments, the water treatmentsystem 200 may include a concentrate discharge system 230 configured todischarge the concentrate reject stream. Further, the concentratere-blending unit 285 may be configured to hold and/or circulate aportion of the concentrate reject stream. Furthermore, as discussedabove, the concentrate re-blending unit 285 may be operatively connectedto the concentrate discharge system 230 and may include a monitorconfigured to monitor characteristics of the concentrate reject stream.

Specifically, in one or more embodiments, the concentrate re-blendingunit 285 may be configured to monitor one or more characteristics of theconcentrate reject stream that has been discharged into the concentratedischarge system 230 and selectively re-blend the concentrate rejectstream into the water intake system based on the identifiedcharacteristics and predefined water-characteristic tolerances of theconcentrate reject stream via a blend line 275 or through theconcentrate re-blending unit 285. In one or more embodiments, the blendline 275 may be operatively connected between the concentrate dischargesystem 230 and the main plant 240. The concentrate discharge system 230and/or the blend line 275 may include a valve that may allow selectivepassage of the concentrate reject stream between the concentratedischarge system 230 and the main plant 240.

In one or more embodiments, valves controlling the aqueous permeatestreams may be controlled in order to control the output of theconcentrate reject stream. In other words, the characteristics andtolerances of the aqueous permeate streams may be monitored and/ormanipulated in order to manipulate and/or control the characteristicsand tolerances of the concentrate reject stream.

As discussed above, in one or more embodiments, at least one of each ofa conductivity sensor 224, a flow sensor 226, and a hardness sensor 227may be disposed on the blend/bypass line 225. In one or moreembodiments, each of the conductivity sensor 224, the flow sensor 226,and the hardness sensor 227 may be disposed on the blend/bypass line 225to measure conductivity, flow, and hardness of water, respectively,passing through the blend/bypass line 225 on each permeate of themembrane pressure vessel. For example, as shown in FIG. 4A, each of theconductivity sensor 224, the flow sensor 226, and the hardness sensor227 may be disposed on the blend/bypass line 225 to measureconductivity, flow, and hardness of water, respectively, in theblend/bypass line 225 after the water passes through each membranepressure vessel 214, 216, 218. Those having ordinary skill in the artwill appreciate that each of the conductivity sensor 224, a flow sensor226, and a hardness sensor 227 may be any conductivity sensor, flowsensor, or hardness sensor known in the art.

Furthermore, in one or more embodiments, the water treatment system 200may include a desalination water controller 265. In one or moreembodiments, the desalination water controller 265 may take signals fromdesalination plant sensors and output signals to the main plant 240.Further, the controller 265 of the water treatment system 200 may beconfigured to automatically re-blend the concentrate reject stream intothe water intake system based on the identified characteristics andpredefined water-characteristic tolerances of the concentrate rejectstream via the blend line 275 or through the concentrate re-blendingunit 285.

Another aspect of the present disclosure is directed to a method fortreating water. The method for treating water may include intaking afirst amount of water from a first source into a plurality of treatmentblocks, treating the first amount of water, outputting aqueous treatedwater streams from each of the plurality of treatment blocks, separatingthe aqueous treated water streams from each of the plurality oftreatment blocks into aqueous permeate streams and concentrate rejectstreams, monitoring each of the aqueous permeate streams, controllingthe operation of at least one of the plurality of treatment blocks basedon predefined water-characteristic tolerances that fall within apredetermined concentration range based on the different qualities ofthe aqueous permeate streams, outputting a product water stream into aninjection water reservoir or blend point, the product water streamcomprising the aqueous permeate stream, intaking a second amount ofwater from a second source into a produced water reservoir, treating thesecond amount of water, and discharging the dischargeable water stream.Treating the first amount of water includes pumping at least a portionof the first amount of water through the plurality of treatment blocks.The monitoring includes identifying different characteristics of theaqueous permeate streams. Treating the second amount of water includescombining the second amount of water with the product water stream intoa dischargeable water stream in the injection water reservoir or at theblend point.

In one or more embodiments, an external water stream from a downholereservoir (i.e., produced water) may be circulated, such as during oilrecovery applications. According to one or more aspects of the presentdisclosure, it may be desirable to control, manipulate, or modify thequality (e.g., the water-characteristics) of the produced water toachieve a predetermined water quality (e.g., specificwater-characteristics) before re-injecting the produced water into theground. Those having ordinary skill in the art will appreciate thatwater quality and water characteristics may include salinity, hardness,turbidity, and/or suspended solids. However, those having ordinary skillin the art will appreciate that any known water characteristic that maybe monitored may be considered to be part of the water quality, and thatwater quality is not limited only to salinity, hardness, turbidity, andsuspended solids.

In order to control, manipulate, or modify the quality of the producedwater to achieve a predetermined water quality, the produced water fromthe reservoir may be monitored and blended with another water streamhaving a specific water quality such that the resulting water streamfrom the combination (e.g., blending) of the produced water from thereservoir and the other water stream will have the predetermined waterquality. In other words, the quality of the produced water may bemonitored, and the information about the quality of the produced watermay cause a water treatment system to produce another water stream to becombined with the produced water such that the resulting, combined waterstream is of a predetermined quality that may be safely re-injected intothe ground.

Referring to FIG. 9, seawater treatment system 900 may include atreatment block 960 that may process and treat water from a water intakesystem 901 and produce a permeate stream and a concentrate stream, ormultiple streams. For example, in one or more embodiments, there may bemultiple treatment blocks, in which each treatment block has a permeatestream and a concentrate stream. Although not shown, the treatment block960 may include membrane pressure vessels, valves, and pumps such asshown in the treatment block 260 of FIG. 4A. Similarly, the water intakesystem 901 may include water intake(s), water intake pump(s),pre-filter(s) such as shown in the water intake system 201 of FIG. 4A.

The permeate stream produced from the treatment block 960 may be atreated water stream, in which intake water was treated in the treatmentblock 960 to produce a water stream having a predetermined waterquality. For example, in one or more embodiments, water taken in by thewater intake system 901 may be treated in the treatment block 960 toproduce a product water stream having a specific salinity and/orhardness. As discussed above, in one or more embodiments, the productwater stream may include the permeate stream, the concentrate stream, ora combination of permeate streams and concentrate streams utilizingdifferent membrane products. For example, in one or more embodiments,the product stream may be the permeate water stream. As shown, theproduct stream may be discharged from the treatment block 960 into ablending point or an injection water reservoir 992. In one or moreembodiments, a valve and/or a flow meter (not shown) may be disposedbetween the treatment block 960 and the injection water reservoir 992and may control fluid communication between the treatment block 960 andthe injection water reservoir 992. Thus, the valve may control thequantity of the treated product stream discharged into the injectionwater reservoir 992. The remaining water that was taken into thetreatment block 960 but not produced in the permeate stream may bedischarged from the treatment block separately in the concentratestream. As shown, the concentrate stream may be collected into aconcentrate discharge system 930.

Further, in one or more embodiments, the seawater treatment system 900may also intake water from other sources separate from the source(s)from which the water intake system 901 draws water. For example, asshown, water may be separately produced from a well reservoir 990. Thosehaving ordinary skill in the art will appreciate that the well reservoir990 may represent multiple reservoirs and is not limited to a singlewell reservoir. This produced water may be drawn into a produced watercollection 991.

The produced water may need to be treated before discharging orre-injecting the produced water into the sea or into the ground. Forexample, in enhanced oilfield applications, an operator may want tore-inject produced water to avoid discharge of the produced water.However, the water quality of the produced water, such as salinity,hardness, turbidity, or other water quality characteristics, may need tobe controlled or manipulated before the produced water may be safelyre-injected. For example, when produced water is collected on a platformduring oil recovery, the produced water may have specialty chemicalsadded, such as one or more chemicals, polymers, surfactants, etc., toimprove oil recovery. Because the produced water may include suchspecialty chemicals, the operator may not want to discharge the producedwater back into the sea or back into the ground. In order to safelydischarge the produced water, the water quality of the produced watermay be controlled or manipulated, as will be described below.Alternatively or additionally, with the proper control or manipulationof the water quality, the produced water may be rendered appropriate forre-injection.

As the produced water is produced from the well reservoir 990, theproduced water may be monitored by a sensor 993A. In one or moreembodiments, the sensor 993A may monitor the quantity of produced wateras well as the produced water quality (e.g., the water characteristics).For example, the sensor 993A may monitor the salinity and hardness ofthe produced water from the well reservoir 990. Further, in one or moreembodiments, the sensor 993A may monitor the turbidity of the producedwater or the suspended solids that may be present in the produced water.In one or more embodiments, the water quality and quantity informationof the produced water obtained by the sensor 993A may be transmitted(e.g., by wireless transmission such as radio or any other transmissionmeans known in the art) to an operator or otherwise to the rest of thewater treatment system 900. Subsequently, the water intake system 901and the treatment block 960 may be controlled or manipulated, and thequantity and quality of water taken into the treatment block 960 anddischarged from the treatment block 960 as the product stream into theinjection water reservoir 992 may be controlled.

The produced water from the produced water collection 991 may betransferred to the blending point or injection water reservoir 992. Inone or more embodiments, a valve and/or a flow meter (not shown) may bedisposed between the produced water collection 991 and the blendingpoint or injection water reservoir 992 and may control fluidcommunication between the produced water collection 991 and the blendingpoint or injection water reservoir 992. Thus, the valve may control thequantity of produced water discharged into the well reservoir 990. Asensor 993B may also be disposed between the produced water collection991 and the injection water reservoir 992 to monitor the quality andquantity of the produced water as the produced water is transferred intothe injection water reservoir 992. The information obtained by thesensor 993B may also be transmitted to an operator of the watertreatment system 900. Also, if the produced water has an appropriatequality for discharge, the produced water may be discharged from theproduced water collection 991.

Subsequently, calculations may be made in view of the information aboutthe produced water obtained by the sensors 993A, 993B, and the waterintake system 901 and treatment block 960 may react, or be controlled ormanipulated, to produce water in the product stream in a specificquantity and water quality such that combining the product stream withthe produced water in the injection water reservoir 992 results in adischargeable water stream of a predetermined water quality. In otherwords, a specific quantity and quality of treated water through thetreatment block 960 may be treated and combined or blended with theproduced water based on the quantity and quality of the produced waterin order to produce a dischargeable water stream of a predeterminedwater quality.

For example, in one or more embodiments, the sensor 993A, 993B maymonitor and transmit the quantity, as well as the hardness and/orsalinity of the produced water produced from the well reservoir 990. Theoperator or the treatment system 900 may then use this information tocalculate how much hardness or salinity may need to be produced in thewater from the treatment block 960 (i.e., how much hardness, salinity,turbidity, etc. may need to be in the product stream) such that when theproduced water is combined with the product stream, a dischargeablewater stream of desirable quality is formed and may be re-injected intothe well reservoir 990 or discharged into the sea or into the ground.

In one or more embodiments, as the dischargeable water stream (which maybe a combination of the produced water and the product stream isre-injected into the well-reservoir 990, a sensor 993C disposed betweenthe injection water reservoir 992 and the well reservoir 990 may ensurethat the proper water quality is monitored. The sensor 993C may allow anoperator or the water treatment system to monitor the quantity andquality of the dischargeable water stream as the dischargeable waterstream is re-injected into the well reservoir 990.

Advantageously, one or more embodiments may provide one or more of thefollowing. In offshore operations, the most common source of injectionwater is seawater, which has significant levels of contaminants that maybe removed before the seawater can be used as an injection water.Depending on the type of formation being drilled, certain components ofthe seawater must be removed while others must remain in order toprotect the formation from damage and to maximize the hydrocarbonsproduced from the formation. Using a combination of water treatmentapproaches may allow for water treatment processes which are able toeffectively and cost efficiently prepare injection water that isspecifically tailored for the formation being drilled and thereby allowsfor improved oil recovery. Further, water quality and specificwater-characteristics can be closely controlled to ensure maximumeffectiveness in varying downhole environments. Also, the watertreatment processes may be used to reduce costs associated with thepreparation of injection water because the most expensive component,i.e., the high-pressure pump, can be operated at variable pressuresusing information from the permeate streams and output streams.

While the invention has been described with respect to a limited numberof embodiments, those skilled in the art, having benefit of thisdisclosure, will appreciate that other embodiments can be devised whichdo not depart from the scope of the invention as disclosed herein.Accordingly, the scope of the invention should be limited only by theattached claims.

What is claimed:
 1. A method for treating water, comprising: intaking afirst amount of water into a first plurality of treatment blocks, thefirst plurality of treatment blocks comprising: one or more reverseosmosis treatment blocks, one or more nanofiltration treatment blocks,both a controllable, variable speed, high-pressure pump, and acontrollable valve associated with each treatment block of the firstplurality of treatment blocks, wherein the one or more nanofiltrationtreatment blocks are in parallel with the one or more reverse osmosistreatment blocks; intaking a second amount of water into a blend linethat bypasses the first plurality of treatment blocks; pre-treating atleast the first amount of water using at least one of a filter and afirst specially-treated water; treating the first amount of water,wherein treating the first amount of water comprises: pumping a firstportion of the first amount of water through the one or more reverseosmosis treatment blocks of the first plurality of treatment blocks,separating the first portion into a first aqueous stream comprising afirst permeate and a second aqueous stream comprising a firstconcentrate, wherein the first aqueous stream is reduced in monovalentand divalent ions and the second aqueous stream is enriched inmonovalent and divalent ions, and pumping a second portion of the firstamount of water through the one or more nanofiltration treatment blocksof the first plurality of treatment blocks, in parallel with the one ormore reverse osmosis treatment blocks, separating the second portioninto a third aqueous stream comprising a second permeate and a fourthaqueous stream comprising a second concentrate, wherein the thirdaqueous stream is reduced in divalent ions and reduced in monovalentions, while the fourth aqueous stream is enriched in divalent ions andenriched in monovalent ions; monitoring each of the first, second,third, and fourth aqueous streams and the fluid from the blend line,wherein the monitoring comprises identifying all of flow rate,conductivity, turbidity, and concentrations of one or more divalent ionsfor each of the first, second, third, and fourth aqueous streams and thefluid from the blend line; controlling an operation of at least one ofthe first plurality of treatment blocks, by controlling thecontrollable, variable speed, high-pressure pump, and the controllablevalve associated with the at least one of the first plurality oftreatment blocks, as a function of predefined water-characteristictolerances that fall within a predetermined concentration range, whereincontrolling comprises modifying at least one of flow rate, pressure,membrane flux, fraction of membranes used, recovery percentage, waterpH, and water temperature, and wherein controlling is capable ofmodifying all of flow rate, pressure, membrane flux, fraction ofmembranes used, recovery percentage, water pH, and water temperature;combining at least two of the first, second, third, and fourth aqueousstreams, a second specially-treated water stream, and the fluid from theblend line at a blend point to form a product water stream based onpredetermined characteristics of the first, second, third, and fourthaqueous streams, the second specially-treated water stream and the fluidfrom the blend line and the predefined water-characteristic tolerances;outputting the product water stream comprising the combined aqueousstreams, wherein the product water stream maintains the predefinedwater-characteristic tolerances within a predetermined concentrationrange, wherein the second amount of water is a produced water from anoil field recovery operation.
 2. The method of claim 1, wherein one ormore of the predefined water-characteristic tolerances fall within aconcentration variation of +/−100 mg/L.
 3. The method of claim 1,further comprising: feeding one or more of the first, second, third, orfourth aqueous streams back into one or more of the first plurality oftreatment blocks.
 4. The method of claim 1, further comprising: mixing athird specially-treated water into the product water stream.
 5. Themethod of claim 1, wherein the method is capable of producing at least100,000 bbl/day of product water.
 6. A method for treating water,comprising: intaking a first amount of water into a first plurality oftreatment blocks, the first plurality of treatment blocks comprising:one or more reverse osmosis treatment blocks, one or more nanofiltrationtreatment blocks, both a controllable, variable speed, high-pressurepump, and a controllable valve associated with each treatment block ofthe first plurality of treatment blocks, wherein the one or morenanofiltration treatment blocks are in parallel with the one or morereverse osmosis treatment blocks; intaking a second amount of water intoa blend line that bypasses the first plurality of treatment blocks;pre-treating at least the first amount of water using at least one of afilter and a first specially-treated water; treating the first amount ofwater, wherein treating the first amount of water comprises: pumping afirst portion of the first amount of water through the one or morereverse osmosis treatment blocks of the first plurality of treatmentblocks, separating the first portion into a first aqueous streamcomprising a first permeate and a second aqueous stream comprising afirst concentrate, wherein the first aqueous stream is reduced inmonovalent and divalent ions and the second aqueous stream is enrichedin monovalent and divalent ions, and pumping a second portion of thefirst amount of water through the one or more nanofiltration treatmentblocks of the first plurality of treatment blocks, in parallel with theone or more reverse osmosis treatment blocks, separating the secondportion into a third aqueous stream comprising a second permeate and afourth aqueous stream comprising a second concentrate, wherein the thirdaqueous stream is reduced in divalent ions and reduced in monovalentions, while the fourth aqueous stream is enriched in divalent ions andenriched in monovalent ions; monitoring each of the first, second,third, and fourth aqueous streams and the fluid from the blend line,wherein the monitoring comprises identifying all of flow rate,conductivity, turbidity, and concentrations of one or more divalent ionsfor each of the first, second, third, and fourth aqueous streams and thefluid from the blend line; controlling an operation of at least one ofthe first plurality of treatment blocks, by controlling thecontrollable, variable speed, high-pressure pump, and the controllablevalve associated with the at least one of the first plurality oftreatment blocks, as a function of predefined water-characteristictolerances that fall within a predetermined concentration range, whereinthe method controls all of flow rate, pressure, membrane flux, fractionof membranes used, recovery percentage, water pH, and water temperature;combining at least two of the first, second, third, and fourth aqueousstreams, a second specially-treated water stream, and the fluid from theblend line at a blend point to form a product water stream based onpredetermined characteristics of the first, second, third, and fourthaqueous streams, the second specially-treated water stream and the fluidfrom the blend line and the predefined water-characteristic tolerances;outputting the product water stream comprising the combined aqueousstreams, wherein the product water stream maintains the predefinedwater-characteristic tolerances within a predetermined concentrationrange, wherein the second amount of water is a produced water from anoil field recovery operation.
 7. The method of claim 6, wherein one ormore of the predefined water-characteristic tolerances fall within aconcentration variation of +/−100 mg/L.
 8. The method of claim 6,further comprising: feeding one or more of the first, second, third, orfourth aqueous streams back into one or more of the first plurality oftreatment blocks.
 9. The method of claim 6, further comprising: mixing athird specially-treated water into the product water stream.
 10. Themethod of claim 6, wherein the method is capable of producing at least100,000 bbl/day of product water.
 11. A method for treating water,comprising: intaking a first amount of water into a first plurality oftreatment blocks, the first plurality of treatment blocks comprising:one or more reverse osmosis treatment blocks, one or more nanofiltrationtreatment blocks, both a controllable, variable speed, high-pressurepump, and a controllable valve associated with each treatment block ofthe first plurality of treatment blocks, wherein the one or morenanofiltration treatment blocks are in parallel with the one or morereverse osmosis treatment blocks; intaking a second amount of water intoa blend line that bypasses the first plurality of treatment blocks;pre-treating at least the first amount of water using at least one of afilter and a first specially-treated water; treating the first amount ofwater, wherein treating the first amount of water comprises: pumping afirst portion of the first amount of water through the one or morereverse osmosis treatment blocks of the first plurality of treatmentblocks, separating the first portion into a first aqueous streamcomprising a first permeate and a second aqueous stream comprising afirst concentrate, wherein the first aqueous stream is reduced inmonovalent and divalent ions and the second aqueous stream is enrichedin monovalent and divalent ions, and pumping a second portion of thefirst amount of water through the one or more nanofiltration treatmentblocks of the first plurality of treatment blocks, in parallel with theone or more reverse osmosis treatment blocks, separating the secondportion into a third aqueous stream comprising a second permeate and afourth aqueous stream comprising a second concentrate, wherein the thirdaqueous stream is reduced in divalent ions and reduced in monovalentions, while the fourth aqueous stream is enriched in divalent ions andenriched in monovalent ions; monitoring each of the first, second,third, and fourth aqueous streams and the fluid from the blend line,wherein the monitoring comprises identifying at least one from a groupconsisting of flow rate, conductivity, turbidity, and concentrations ofone or more divalent ions for each of the first, second, third, andfourth aqueous streams and the fluid from the blend line wherein themonitoring is capable of identifying all of flow rate, conductivity,turbidity, and concentrations of one or more divalent ions for each ofthe first, second, third, and fourth aqueous streams and the fluid fromthe blend line; controlling an operation of at least one of the firstplurality of treatment blocks, by controlling the controllable, variablespeed, high-pressure pump, and the controllable valve associated withthe at least one of the first plurality of treatment blocks, as afunction of predefined water-characteristic tolerances that fall withina predetermined concentration range, wherein the method controls all offlow rate, pressure, membrane flux, fraction of membranes used, recoverypercentage, water pH, and water temperature; combining at least two ofthe first, second, third, and fourth aqueous streams, a secondspecially-treated water stream, and the fluid from the blend line at ablend point to form a product water stream based on predeterminedcharacteristics of the first, second, third, and fourth aqueous streams,the second specially-treated water stream and the fluid from the blendline and the predefined water-characteristic tolerances; outputting theproduct water stream comprising the combined aqueous streams, whereinthe product water stream maintains the predefined water-characteristictolerances within a predetermined concentration range, wherein thesecond amount of water is a produced water from an oil field recoveryoperation.
 12. The method of claim 11, wherein one or more of thepredefined water-characteristic tolerances fall within a concentrationvariation of +/−100 mg/L.
 13. The method of claim 11, furthercomprising: feeding one or more of the first, second, third, or fourthaqueous streams back into one or more of the first plurality oftreatment blocks.
 14. The method of claim 11, further comprising: mixinga third specially-treated water into the product water stream.
 15. Themethod of claim 11, wherein the method is capable of producing at least100,000 bbl/day of product water.